Test-run dashboards auto-refresh when processing finishes

Test-run dashboards in the web UI no longer get stuck on the “processing” spinner after a run actually finishes. Previously, finished runs could remain stuck appearing as processing even when the backend already considered them complete, and the page would only update on a manual refresh. The completion event is now reliably delivered to the web tier (relayed via Oban to a clustered web node, plus a polling fallback in the test-run detail page), so dashboards refresh themselves when processing completes on the xcresult-processor.